DE1483089B1 - Shaft furnace charged from above for burning heat-sensitive material, especially lime, with a preheating zone, a burning zone and a cooling zone - Google Patents

Description

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The invention relates to a top-down flow of the material to be fired through the furnace

sent shaft furnaces for the burning of heat and other the combustion problems of the gas

sensitive material, especially lime, with a ses and its distribution in the firing beds

Preheating zone, a burning zone and a cooling zone met.

with a downward-facing burner device, with a 5 Thus British patent specification 742 802 shows a

directions for withdrawing gases from the cooling shaft furnace with an inside arranged

zone into the combustion zone and from the combustion zone into the roof- or hood-shaped deflector and a

Preheating zone, these gases in the cooling zone blower, which the proportion of the combustion chamber

and should increase in the preheating zone of the shaft furnace in the counter-mer downward flowing gas, since

current, in the combustion zone but in direct current 10 due to the shaft profile there a large part

will. of the gases emerging from the combustion chamber

Nowadays there are two commonly used han- dical ways up,

The usual facilities for the production of lime, despite the intended fan, however, is hardly

namely the rotary kiln and the shaft furnace. of a direct current of gases and material to be fired

The rotary kiln is probably the one in Northern 15 speaking, since only about 50% of the gases are most widespread in America, although the disadvantages are the hoped-for flow direction,
relatively high investment costs and a relatively low fuel yield from a shaft furnace is described in the Austrian patent specification 202918, which has approximately 30 to 35%. However, it allows a moderately distributed over the circumference, parallel to the shaft very precise control of the product. ao furnace arranged combustion chambers, which are from top to bottom

The shaft furnace has the bottom lead at relatively low, the shaft furnace has to be fired

Investment costs have the advantage of a much larger required hot gases. Internally

mechanical simplicity and a low mechanical shaft furnace, the gases flow in the material to be fired

nical maintenance effort with comparative countercurrent from bottom to top,

wise high fuel yield of 50 to 75%. Each 35 The invention is based on the object for

but there was a shaft furnace with an advantageous gas flow in the case of the vertical shaft furnace

always several control problems, such as creating an arrangement in which within the channels,

the gas flow or gas channel formation, which lead to one in which hot gases, no as a result of the

uneven heat distribution and high gas temperatures, experience has shown to be disruptive

inconsistent or unevenly fired er-30 susceptible fan is required.

to bear witness. According to the invention, this object is achieved

Another disadvantage of the average proposed is that a reduction in cross section

Deten construction of the shaft furnace is that the above the burner device and above the

Fuel in gaseous form is placed in the gaps or spaces of the combustion zone, with the diminished

is introduced between the items to be fired, whereupon the passage cross-section is less than or equal to 25%

This fuel mixes with air and is the free shaft furnace cross-section.

standing burn mainly in the gaps The length of the draft is

takes place between the items to be fired. It is demonstrably advantageously at least equal to the distance

bar that the difficulty to get a thorough check from the lower edge of the burner chamber to the

to achieve mixing of the air with the fuel, 40 outlets from the combustion zone to the preheating zone,

largely the cause of the undesired gas flow- The gas outlet from the preheating zone is purposeful-

tion is, d. H. the difference in heating from moderately between the furnace loader

Dividing the material to be fired with further irregularities and the gas inlet in the preheating zone.

or unevenness in the end product. arranges.

Most shaft furnaces are 45 on their upper side due to the reduction in cross-section.

charged with material to be fired, whereby the combustion gases called pressure difference can promote the

from bottom to top, i.e. in the countercurrent process, gases from the combustion zone are used,

brush through the oven. In general, the shaft furnace is always expedient

assumed that to achieve a high one should be built so that at least one side of the

Efficiency in an endothermic process, 50 furnace an access to the burner device is provided

such as the burning of lime, is a counter- is.

would have to use electricity method. However, the burner device can be selected from a plurality

found that the countercurrent effect caused by spaced apart burners

Gases with the highest temperature exist in the material to be fired.

brings into contact at its highest temperature, 55 The reduction in area can be achieved by a

one of the causes of the gas channel formation and the non-plurality of essentially vertically arranged,

uniformity of the end product. the burner device enclosing passages

On the other hand, it has been found that an equal will be formed.

Electricity firing or heating, in which the gases are This arrangement is in every way operationally higher temperature with the low temperature 60 _and does not require any additional effort. The Brenngm come into contact, the dead burning of the opposite is the blower after the said briti product makes almost impossible and to a very see patent temperature-sensitive and repagiform temperature over the entire hot raturensendens. It requires special costs to lead to AnZone. Creation and its operation, and - that is

One of the most essential points for resolving the aforementioned difficulties - when it comes to finding out numerous different proposals for the construction case, the operation is disrupted. As soon as no suction became known of vertical shaft furnaces, of more done, on the one hand that in the combustion zone which destroys some mechanically controlled material, and kicks on the other

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no preheating of the freshly supplied material to equalize the temperature of all parts of the firing material. This deficiency is in the present er- so that the gas channel formation is eliminated,
finding avoided with certainty. As discussed above, it should be noted that the furnace according to the invention works as follows: Gas channel formation in the previously known types Via the inlet openings on the underside of the 5 of the shaft furnace, a natural sequence of the Ver-cooling zone, which is the last stage in the downward burning of the fuel is in the cavities in the flow of limestone in the course of the burning process inside the kiln. It makes sense that air is being sucked in. This fresh air is in contact with the air where the fuel comes into contact with the cooling of the freshly produced lime in the cooling area and mixes and burns with it, zone in countercurrent at least partially via the io between the gas and air flows -Auction openings in the cooling zone are sucked off and formed with a surface at which a high temperature develops with the help of suitable pressure-generating means in the combustion zone. Since the flow resistance for the high zone, pressed to support the maximum temperature gases, is greater than for low temperature combustion of the fuel gases introduced at this point, there is a natural tendency for the heavy substances. The hot combustion gases then come 15 most gases to sweep through the Brenngutbett, ie, directed downwards in cocurrent together with the fact that the air to the coolest points in the Brenngutfluss in contact with the limestone, which flows, so that the bed dynamically unstable is.
by their partial suction through the lower suction openings is consequently a further advantage of the invention. The restricted heating of the material to be fired with the products of a passage between the adjacent preheating zone ao complete combustion from a heating burner and the firing zone creates a pressure so that or furnace. It is clear that the heating of the hot air with the gases from the combustion in a countercurrent furnace with products from a complete cocurrent (with the fuel flow) downward combustion at very high temperatures and through the fuel to the outlet openings leads to difficulties leads to the refractory structure, pressing is carried out without the aid of additional mechanical devices. Firing with the heating with products from a The hot gases, which then in countercurrent through the complete combustion, which allows the above-described openings leading into the preheating zone, a construction method.

can be brought at much higher temperature. An embodiment of the invention is in the

doors than shown in the previously known shaft furnace construction drawing and will be explained in more detail below

species are promoted as one is directly described on them. It shows

Acting fan is not required. After F i g. 1 is a front view of a vertical furnace

the gases get into the preheating zone and through the downward directed according to the invention

the upper layer of the items to be fired are swept through, the flow of the items to be fired,

they are removed from the discharge openings of the preheating 35 F i g. 2 a side view of the furnace construction at Ver

zone, preferably with the help of an external blower, illustration of the line and blower unit,

discharged. F i g. 3 shows an embodiment of the furnace in

It should be noted that the fuel in a Feue- matic representation, illustrating the

chamber with high heat emission completely eliminates the flow of combustion gases,

is burning and that only the combustion products 40 F i g. 4 a horizontal section according to the

be passed through the limestone kiln. The line 4-4 in Fig. 2,

fundamental laws governing gas flow F i g. 5 shows another embodiment of the furnace

result from the equation in a schematic representation with another

__ firing arrangement,

P - Ldu, ₄₅ Fig. 6 is a graph of the intensity

in the flame temperature versus time.

P = pressure drop according to FIG. 1 to 3 consists of the furnace according to the

C = a constant invention with downward fuel flow

u = the speed of the gas, ff ^e ™ ^e ™ elongated cylindrical shaft 10. The

d = the density of the gas ⁵ ° ^shaft t ^ls tm divided into three main parts, ie the

Preheating zone 20, the burning zone 30 and the cooling zone

means. 40. The jacket of the main shaft 10 is lined on its inner side with highly heat-resistant fire, the density of which changes inversely with the absolutely solid bricks 12.
Temperature. As a result, the volume and weight of the limestone will increase with the speed for any given help one with the preheating zone directly in gas weight. Connected funnel 14 in the It makes sense that when doubling the tem- furnace introduced. The preheating zone is halved by the temperature of the gas density and its speed burning zone 30 is doubled by reducing the interior space. Since the speed 60 of the furnace is separated, which in its cross-section factor occurs in the square in the equation, the restricted passage 22 is formed. The preheating zone 20 pressure drop V »· (2) ² or twice as high. Accordingly, it has gas inlet openings 24 which, according to the interior, lead high-temperature gases to the flow of the furnace and, with an outer ring line, have a higher resistance than low-temperature gases. 25 and a connecting line 26 in connection. By heating with combustion products, the 65 are connected, which, as will be described in more detail below, allow the lowest flow of the parts of the fuel to be cooled, allow hot gases to escape from the flow resistance and draw the greatest volume of the combustion zone get into the preheating zone and the gases off, whereby they have the tendency to reduce the temperature of the limestone when preparing for

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increase its treatment in the burn zone 30. The cooling zone 40 of the furnace is below the on the outside of the furnace to one over the combustion zone 30 and contains in the lower section of the Zone 20 extending suction line 28 connected to the main air intake openings 41 and above the furnace senes fan 27 is used to discharge the exhaust gas suction openings 41 air outlet openings 42, the after their preheating. The line 28 bisects the 5 with a wind ring or a ring line 47 to a cross section the preheating zone of the furnace work together in one. The wind ring or the ring line A relatively short distance above the hot 47 is via the line 44 with the furnace fan gas inlet ports 24. Connected on the bottom of 56. With this arrangement, the cooling line 28 a slot 28 a is provided for the sheep air after it passes through the cooling zone 40 an unobstructed passage for the exhaust gases. io is deleted, fed to the combustion chamber 38.

In the burning zone 30 is an inward The lime produced in the kiln is with the help

extending radial wall portions 32 supported firing of an ordinary rotary feeder

chamber 38 arranged. At this point, the 45 and one hopper 46 transport means are

Furnace walls, as shown in FIG. 1 and 2 can be seen, controls supplied, which are available under the furnace,

cut so that with the help of the support walls 32 15 In Fig. 5, another embodiment is one

Access routes 33 arise, which represent a relatively furnace according to the invention. With this one

Another design of the firing zone is the convenient access to the maintenance of the furnace

chamber 38 allow. predominant characteristic. Instead of a centrally

Between the access paths 33 are from the orderly combustion chamber are in the inside

Passages 22 formed shafts are provided, the 20 inclined furnace walls 111 several burners

the preheating zone 20 attached to the internal zone 30 connects the 131st In this case the fuel

the. As in Fig. 4 shown in detail, and air nozzles 151 and 152 in the vicinity of the outer

the passages 22 through the supporting walls 32 side of the wall 111 attached, the refractory

of the access route, the wall parts 11 of the kiln brick 112 are arranged around the nozzles in such a way (from

and determined on the inside by the walls 34. 25) are formed in that they have combustion chambers 138

Of course, all of these walls are up.

the inside of the furnace with refractory bricks 12 To adapt to the main features of the invention

disguised. The purpose of the limited limestone paving must be the main culvert 135 between the

Passages 22 is the creation of a restriction heating zone 120 and the burning zone 130 accordingly

for the upward movement of the furnace 30 to be limited to a considerable extent. this will

Exiting hot gases chamber, so that the gases reached by constriction of the walls 111 of the

be forced to take their predetermined path of the furnace at a point immediately above the furnace

to follow. ner 131. Immediately above the constricted

The annular firing chamber 38 is, as in section or passage 135 , the walls 111

F i g. 3 shown, offset backwards to create 35 outwardly inclined in such a way that the

sufficient space for the complete formation of lost firing material in the furnace

Combustion of fuel and air that is minimized from a

fuel nozzle leading into the combustion chamber

51 or one in the rear section of the Feue mode of operation

chamber 38 attached air duct 52 from 40 in the production of lime using

step. The air duct 52 is connected to an external fan of the furnace type according to the invention

56 connected to provide a pressure supply. Limestone using the standardized funnel 14

In this introduced into the furnace 10 in the radial direction through the walls 53. The limestone moves

delimited chamber 38 is a complete one in the furnace during the entire operation,

Incineration takes place. 45 as indicated by the dashed arrows, below

At a distance dl from the combustion chamber its own weight downwards. Thus wandered through

38 equal to the distance d between the furnace he each treatment zone of the furnace with a ge

chamber 38 and the top of the limited speed, which is with the help of the at the bottom

Passages 22 are in the walls of the furnace hot control mechanism 45 arranged in the furnace

gas outlet slots or openings 39 are provided. 5 ° is regulated. It is also clear that the KaIk-

The openings 39 lead into a ring stone or collecting stone in the furnace so that it can be piles up completely

line 36, which fills via line 26 to the in the.

Upper ring line 25 leading to the preheating zone

closed is. caused pressure difference through the openings 41

It goes without saying that each of the combustion gases 55 sucked into the furnace by being fed through the full

conveyed gas pressure from the combustion chamber from solid arrows according to FIG. 3 illustrated way

the same gas velocity in both directions follows. So you let cool air through the cooling zone

causes. By restricting the cross-sectional area 40, flow around the granular material present there.

of the furnace shaft above the combustion chamber to cool the product. After the

38 suction caused to about 25% of the cross-sectional area of the main 60 fan 56, the air is closed

Well 10 or less is the total gas exit openings 42 above the inlet openings

mass flow of combustion products sucked out of the 41. So the air moves as the

Firing chamber 38 slowly moved down into the preheating zone 20 after limestone, to the combustion

above 20% and through the combustion zone 30 downwards good flow in countercurrent. The fan 56 sucks the

80%. As a result, it can be said that the actual air from the ring line 47 via the line 44 to

borrowed processes in the combustion zone 30 of the furnace and pushes them into the combustion chamber 38.

The air thus supplied to the furnace chamber 38 is approximately 80% in relation to the flow of fuel

flow and 20% countercurrent. is supplied via the line 51 with oil or

Natural gas mixed for complete combustion in the combustion chamber 38, which is in the central part the burning zone 30 is open at the bottom. Meet the combustion products from the combustion chamber directly on the preheated limestone, which is limited by the leading from the preheating zone 20 Passages 22 are introduced into the combustion zone 30. The combustion products flow down the combustion or hot zone 30, then through the openings 39 into the hot gas ring line 36, from which they exit at temperatures of about 1000 to 1300 ° C., fed to the preheating zone 20 to become.

As they flow through the combustion zone 30, the gases reach the openings 39 in one Distance below the firing chamber 38, so that they are in one direction in cocurrent with the Flow of the material to be fired.

With this arrangement it is possible that the combustion products enter the combustion chamber 38 at ao Leave temperatures of around 1550 to 1750 ° C. Flame weakening or circulation is with that Oven system with downwardly directed Brenngutfluss usually not required, since when the high temperature gases come into contact with unburned limestone immediately through the firing process be cooled so that the material to be fired cannot burn to death. If extremely precise Control, for example in the case of unusually heat-sensitive items to be fired, is required, one could partly use a fuel gas cycle.

The effect of this arrangement on the firing process is clearly indicated in the curves shown in FIG. 6 which illustrate the temperature relationship between the material to be fired and the gas. The curve for the furnace with a direct current hot zone shows that the firing process takes place over an extended period of time at a uniformly low temperature ρ 2. The considerable heat voltage (tremendous heat potential) develops between the combustion products from the combustion chamber 38 at around 1650 ° C and the preheated firing material at around 950 ° C, a difference of 750 ° C, which leads to extremely high heat transfer speeds at a time when the high CO ₂ content of the lime makes it impossible to burn it to death. Of course, the material to be fired cannot be heated above the temperature of the gases, so that the longer the effective hot zone, the lower the final temperature of the firing process. Lime burning is a highly endothermic process and as long as CO _{2 is} evolving it is difficult to overheat the lime. The curves g1 and p1 each show the temperature of the gases or the flames in relation to the temperature of the material to be fired, illustrating the critical situation caused by a standard furnace, which easily leads to the material being burned to death.

Even if the material to be burned is finished before it leaves the firing zone 30, it is only in contact with the coolest gases and cannot burn to death, so that the material to be burned in order to ensure complete burning of the entire material to be burned over an extended period of time the burning zone 30 can be left. The overall result of the design with direct current and downward flow of fuel in the firing zone is a furnace that naturally does not have any gas flow or gas channel formation and cannot lead to dead burning of the firing material. Due to the efficiency of the heat transfer and the lack of overlap in the combustion and in the preheating zone, it can be assumed that the fuel yield is in the range of 1007,960 Kcal _IT per tonne of calcium-rich lime.

Another result of direct current firing is that it migrates into the combustion zone The material to be fired comes into contact with the hottest gases and the gases proportionally with it its sinking in the furnace become cooler, so that prematurely finished firing material does not increase hotter, the material to be fired is exposed to deadly gases.

As described, the hot gases are from the wind ring line 36 via the line 26 to the ring line 52 and passed through the openings 24 into the preheating zone 20. To push through of the extremely hot gases through line 26, no fan is required because of the pressure differential maintained by the high pressure achieved in the combustion zone 30 and by the external fan 56 will. The hot gases flowing into the preheating zone preheat the limestone in preparation for the burn zone. The cheapest method of passing gases through the preheat zone is the countercurrent process that, as can be seen from the drawing, is achieved in that the Suction line 28 is arranged above the inlet openings 24 in the preheating zone.

Claims (7)

Patent claims: 1. Shaft furnace fed from above for burning heat-sensitive material, in particular Lime, with a preheating zone, a burning zone and a cooling zone, with a downward-facing Burner device, with devices for extracting gases from the cooling zone in the combustion zone and from the combustion zone into the preheating zone, with the gases in the cooling zone and in the preheating zone of the shaft furnace in countercurrent, but in the combustion zone in cocurrent are performed, characterized in that that a cross-sectional reduction (22) is arranged above the burner device (38) and above the combustion zone (30), wherein the reduced passage cross-section less than or equal to 25% of the free shaft furnace cross-section is. 2. Shaft furnace according to claim 1, characterized in that the reduced passage cross-section is about 25% of the free shaft furnace cross-section. 3. Shaft furnace according to claim 1 to 2, characterized in that the length (rf) of the cross-sectional reduction (22) at least equal to the distance (rf 1) from the lower edge of the combustion chamber (38) up to the outlets (39) from the combustion zone (30) to the preheating zone (20). 4. Shaft furnace according to claim 1 to 3, characterized in that at least on one side of the furnace an access (33) to the burner device is provided. 5. shaft furnace according to claim 1 to 4, characterized in that the burner device is a 909583/118 A plurality of spaced apart burners (131) . 6. Shaft furnace according to claim 1 to 5, characterized in that the cross-section reduction by a plurality of substantially vertically arranged, the burner device enclosing passages (22) is formed. 10 7. Method for firing heat sensitive material in a shaft furnace according to a of claims 1 to 6, characterized in that as a result of the reduction in cross section (22) adjusting pressure difference exclusively for generating a direct current in the burning zone (30) is used. 1 sheet of drawings